Academic literature on the topic 'Brønsted acid/base'
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Journal articles on the topic "Brønsted acid/base"
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Tan, Choon-Hong, Bo Teng, and Wei Lim. "Recent Advances in Enantioselective Brønsted Base Organocatalytic Reactions." Synlett 28, no. 11 (2017): 1272–77. http://dx.doi.org/10.1055/s-0036-1588847.
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Enantioselective Brønsted base catalyzed reactions have established themselves as powerful tools for the construction of optically pure compounds. Most strategies aim at improving these reactions involve the modification of substrates to decrease the pK a of the acidic proton. Typically, an electron-withdrawing group such as an ester or a fluorine is placed at the α-carbon, where the proton is also residing. The activation of less active proton, thus, becomes a major challenge in this field of research. In order to overcome this pK a barrier, some new innovative approaches have been demonstrated in recent years. The implementation of dual activation modes and the development of organocatalytic Brønsted superbases are selected to be discussed in this minireview.1 Introduction2 Dual Activation Using Lewis Acid and Brønsted Base3 Dual Activation Using Iminium Catalyst and Brønsted Base4 Chiral Brønsted Superbase5 Chiral Ion-Pair Brønsted Base6 Summary and Outlook
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Shen, Juan, and Choon-Hong Tan. "Brønsted-acid and Brønsted-base catalyzed Diels–Alder reactions." Organic & Biomolecular Chemistry 6, no. 18 (2008): 3229. http://dx.doi.org/10.1039/b809505c.
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Nuthakki, Bharathi, Tamar L. Greaves, Irena Krodkiewska, et al. "Protic Ionic Liquids and Ionicity." Australian Journal of Chemistry 60, no. 1 (2007): 21. http://dx.doi.org/10.1071/ch06363.
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Protic ionic liquids (PILs) are a subset of ionic liquids formed by the equimolar mixing of a Brønsted acid and a Brønsted base. PILs have been categorized as poor ionic liquids. However, the issue of assessing the ionicity of PILs is still a matter of debate. In this work we studied some physicochemical properties of three chosen PILs, namely, ethanolammonium acetate (EOAA), 2-methylbutylammonium formate (2MBAF), and pentylammonium formate (PeAF), at the initial equimolar (stoichiometric) acid/base ratio and in the presence of excess acid and base. DSC phase-transition studies along with NMR, IR, and Raman spectroscopy were performed on the chosen PILs. The results are discussed in terms of the degree of ionization (extent of proton transfer from the Brønsted acid to Brønsted base), and the possibility of the formation of polar 1:1 complexes and larger aggregates in the neat stoichiometric PILs.
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Handa, Sachin, Sri S. Subramanium, Aaron A. Ruch, Joseph M. Tanski, and LeGrande M. Slaughter. "Ligand- and Brønsted acid/base-switchable reaction pathways in gold(i)-catalyzed cycloisomerizations of allenoic acids." Organic & Biomolecular Chemistry 13, no. 13 (2015): 3936–49. http://dx.doi.org/10.1039/c4ob02640c.
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Shelly, Kevin P., K. Nagarajan, and Ross Stewart. "Arylphosphonic acids. II. General acid and general base catalysis of acetone enolization." Canadian Journal of Chemistry 65, no. 8 (1987): 1734–38. http://dx.doi.org/10.1139/v87-291.
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We have measured the rate constants for the enolization of acetone catalyzed by 29 arylphosphonate dianions (ArPO32−) and by 20 arylphosphonic acids (ArPO3H2). An excellent Brønsted correlation is found for the former reaction, with most ortho substituted compounds falling on the line drawn for the meta and para compounds (β = 0.72). The largest deviation is found for o-iodo, whose small positive deviation is ascribed to a polarizability effect in the transition state. The arylphosphonic acids give a fairly good Brønsted plot (α = 0.37) but here the ortho substituents tend to react slightly faster than would be expected on the basis of their equilibrium acid strengths. Catalysis by the monoanion ArPO3H− is difficult to detect; such ions appear to be acting as general acids, not general bases, and do not appear to act as bifunctional catalysts; it is shown that protonating acetone is 3.4 × 104 times as effective as deprotonating ArPO3H−. The Brønsted coefficients (β) for the rate-controlling steps for the enolization of acetone by the principal routes are shown to be inversely related to the magnitude of the rate constants.
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Sodeoka, Mikiko, and Yoshitaka Hamashima. "Acid-base catalysis using chiral palladium complexes." Pure and Applied Chemistry 78, no. 2 (2006): 477–94. http://dx.doi.org/10.1351/pac200678020477.
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Chiral Pd aqua and µ-hydroxo complexes were found to act as mild Brønsted acids and bases, and chiral Pd enolates were generated from these complexes even under acidic conditions. Highly enantioselective Michael addition, Mannich-type reaction, fluorination, and conjugate addition of amines have been developed based on the acid-base character of these Pd complexes.
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Chhabra, Tripti, Ashish Bahuguna, Sandeep Singh Dhankhar, C. M. Nagaraja, and Venkata Krishnan. "Sulfonated graphitic carbon nitride as a highly selective and efficient heterogeneous catalyst for the conversion of biomass-derived saccharides to 5-hydroxymethylfurfural in green solvents." Green Chemistry 21, no. 21 (2019): 6012–26. http://dx.doi.org/10.1039/c9gc02120e.
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Sulfonated graphitic carbon nitride having both Brønsted base and Brønsted acid sites is used as a heterogeneous catalyst for the selective conversion of different biomass-derived saccharides to 5-hydroxymethylfurfural in green solvents.
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Ingleson, Michael, and Valerio Fasano. "Recent Advances in Water-Tolerance in Frustrated Lewis Pair Chemistry." Synthesis 50, no. 09 (2018): 1783–95. http://dx.doi.org/10.1055/s-0037-1609843.
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A water-tolerant frustrated Lewis pair (FLP) combines a sterically encumbered Lewis acid and Lewis base that in synergy are able to activate small molecules even in the presence of water. The main challenge introduced by water comes from its reversible coordination to the Lewis acid which causes a marked increase in the Brønsted acidity of water. Indeed, the oxophilic Lewis acids typically used in FLP chemistry form water adducts whose acidity can be comparable to that of strong Brønsted acids such as HCl, thus they can protonate the Lewis base component of the FLP. Irreversible proton transfer quenches the reactivity of both the Lewis acid and the Lewis base, precluding small molecule activation. This short review discusses the efforts to overcome water-intolerance in FLP systems, a topic that in less than five years has seen significant progress.1 Introduction2 Water-Tolerance (or Alcohol-Tolerance) in Carbonyl Reductions3 Water-Tolerance with Stronger Bases4 Water-Tolerant Non-Boron-Based Lewis Acids in FLP Chemistry5 Conclusions
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Wei, Wei, Rongjie Lu, Haojie Xie, et al. "Selective adsorption and separation of dyes from an aqueous solution on organic–inorganic hybrid cyclomatrix polyphosphazene submicro-spheres." Journal of Materials Chemistry A 3, no. 8 (2015): 4314–22. http://dx.doi.org/10.1039/c4ta06444e.
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Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) submicro-spheres were easily prepared, which exhibited a selective adsorption and separation of dyes that can be classified as Lewis acids and/or Brønsted acids by acid–base interactions.
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Catalán, Javier, and José Palomar. "Gas-phase protolysis between a neutral Brønsted acid and a neutral Brønsted base?" Chemical Physics Letters 293, no. 5-6 (1998): 511–14. http://dx.doi.org/10.1016/s0009-2614(98)00833-1.
Full textDissertations / Theses on the topic "Brønsted acid/base"
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Lindsay, Anita Geraldine. "Mechanism-guided studies of Brønsted acid and base organocatalysis." Thesis, Durham University, 2010. http://etheses.dur.ac.uk/314/.
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We have studied the mechanism of the reaction of N-Boc imines and acetylacetone in the presence and absence of chiral phosphoric acid catalysts. In order to gain mechanistic insight into the asymmetric Mannich reaction, a structurally homologous series of N-Boc imines and BINOL-derived phosphoric acid and thiophosphoric acid catalysts were synthesised. The degree of asymmetric catalysis was evaluated by chiral HPLC analysis of the products of catalysed Mannich reactions. Knowledge of the acidity difference between the phosphoric acid catalysts and the iminium ions is essential in order to determine the likely extent of proton transfer, full or partial, between these two species in the course of the Mannich reaction. The determination of aqueous pKa values of iminium ions was attempted by construction of pH-rate profiles for hydrolysis using UV-Vis spectrophotometry. Estimates of the second-order rate constant for acid-catalysed hydrolysis (kH, M-1s-1) and the first-order rate constant for the solvent reaction (k0, s-1) for each imine were extracted from the rate-profiles, however, pKa values could not be obtained for reasons that will be discussed. Iminium ion pKa values were determined in dimethyl sulfoxide by adopting a bracketing indicator method with use of UV-Vis spectrophotometry and pKa values in the range 0.65-1.61 were observed for the series of N-Boc aryl iminium ions. The pKa values of (thio)phosphoric acid catalysts were also estimated in dimethyl sulfoxide using this approach and values in the range 2.21-3.86 were obtained. The determination of pKa values of phosphoric acids in water and acetonitrile was unsuccessful due to the poor solubility of the catalyst in these media. Rate constants for the uncatalysed Mannich reaction of each imine with acetylacetone have been quantified using 1H NMR spectroscopy in CD2Cl2, CDCl3 and CD3CN. It was found that the solvent effect on the rate of the Mannich reaction was small, with the fastest reaction occurring in CD3CN. Altering the imine substituent was found to have a larger effect on the rate. We also aimed to determine rate constants for the catalysed Mannich reaction using 1H NMR spectroscopy. However, in all cases complete hydrolysis of the imine substrate occurred before the first time-point could be obtained. All efforts to suppress hydrolysis proved unsuccessful. Azolium ion organocatalysts were also investigated. These are the conjugate acids of N-heterocyclic carbenes, a class of highly successful nucleophilic/Brønsted base organocatalysts. As these carbenes are generated in situ from azolium ions during organocatalytic reactions, knowledge of the acidity of the parent ion is much sought after. This thesis describes the determination of aqueous pKa values of imidazolium and triazolium ions using a kinetic approach. Second-order rate constants for the deprotonation of these azolium ions by deuterioxide ion (kDO, M-1s-1) in D2O at 25 C were determined by 1H NMR spectroscopy. These kDO values could be used to calculate values for kHO (M-1s-1), the second-order rate constant for deprotonation of the azolium ion by hydroxide ion to give the carbene/ylide in water. Evidence is presented that the reverse rate constant for carbene protonation by solvent water is limited by solvent reorganisation and occurs with a rate constant of kHOH = kreorg = 1011 s-1. Values for kHO and kHOH permitted the calculation of reliable carbon acid pKa values for ionisation of the azolium ions in water. The effects of the N-substituents and counter ion on kHO and pKa values are discussed. Of the triazolium ions studied, kDO values of 3.66 × 107- 6.47 × 108 M-1s-1 were observed with corresponding pKa values of 16.6-17.8. For N,N-dialkylated imidazolium ions, kDO values of 1.03 × 102 - 1.07 × 102 M-1s-1 were obtained which yielded pKa values of 23.3-23.4.
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Clot, Almenara Lidia. "Immobilization of Chiral Brønsted Acids and Lewis Bases for Batch and Flow Enantioselective Catalysis." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/552409.
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El següent treball, titulat “Immobilització d’àcids de Brønsted i bases de Lewis quirals per catàlisi asimètrica en batch i flux”, esta basat en el disseny de nous materials organocatalítics suportats i en la seva aplicació en reaccions asimètriques.
La tesi presenta una discussió detallada de diverses rutes sintètiques per a la immobilització en poliestirè d’àcids de Brønsted i bases de Lewis. En particular, s’ha aconseguit optimitzar una ruta directa i efectiva per a la preparació d’àcids fosfòrics quirals (CPA) i N,N’-diòxids suportats en poliestirè (PS).
Per a realitzar la immobilització s’ha dut a terme un estudi exhaustiu amb la finalitat d’escollir la manera més efectiva de modificar el catalitzador homogeni i emprar el linker més adequat. Les característiques d’aquests nous catalitzadors permeten la seva aplicació en sistemes de flux continu, contribuint d’aquesta manera a millorar la sostenibilitat dels processos catalítics.
L’efectivitat dels catalitzadors d’àcids fosfòrics quirals immobilitzats, en termes d’activitat catalítica, selectivitat i reciclatge, s’ha comprovat en reaccions d’alilació d’aldehids i en la desimetrització de meso-1,3-diones. Els bons resultats obtinguts ens han incentivat per la implementació de sistemes de flux continu, on aquests catalitzadors han demostrat la seva estabilitat.<br>El siguiente trabajo, titulado “Inmovilización de ácidos de Brønsted y bases de Lewis quirales para catálisis asimétrica en batch y flujo”, está basado en el diseño de nuevos materiales organocatalíticos soportados y en su aplicación en reacciones asimétricas.
La tesis presenta una discusión detallada de varias rutas sintéticas para la inmovilización en poliestireno de ácidos de Brønsted y bases de Lewis. En particular, se ha conseguido optimizar una ruta directa y efectiva para la preparación de ácidos fosfóricos quirales (CPA) y N,N'-dióxidos soportados en poliestireno (PS).
Para realizar la inmovilización se ha llevado a cabo un estudio exhaustivo con el fin de elegir la manera más efectiva de modificar el catalizador homogéneo y emplear el linker más adecuado. Las características de estos nuevos catalizadores permiten su aplicación en sistemas de flujo continuo, contribuyendo de esta manera a mejorar la sostenibilidad de los procesos catalíticos.
La efectividad de los catalizadores de ácidos fosfóricos quirales inmovilizados, en términos de actividad catalítica, selectividad y reciclaje, se ha comprobado en reacciones de alilación de aldehídos y en la desimetrización de meso-1,3-dionas. Los buenos resultados obtenidos nos han incentivado a implementar de sistemas de flujo continuo, donde estos catalizadores han demostrado su estabilidad.<br>The following work, entitled “Immobilization of chiral Brønsted acids and Lewis bases for batch and flow enantioselective catalysis”, deals with the design of new supported organocatalytic materials and their application in asymmetric reactions.
The thesis presents a detailed discussion of several synthetic routes for polystyrene immobilization of Brønsted acids and Lewis bases. In particular, it has been possible to optimize a direct and effective route for the preparation of chiral phosphoric acids (CPA) and N,N'-dioxides supported on polystyrene (PS).
To carry out the immobilization, an exhaustive study has been carried out in order to choose the most effective way to modify the homogeneous catalyst, employing the most suitable linker. The characteristics of these new catalysts allow their application in continuous flow systems, contributing in this way to improve the sustainability of the catalytic processes.
The effectiveness of immobilized chiral phosphoric acid catalysts, in terms of catalytic activity, selectivity and recycling, has been proven in allylation reactions of aldehydes and in the desymetrization of meso-1,3-diones. The good results obtained have motivated us to study the implementation of continuous flow systems, where these catalysts have demonstrated their robustness.
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Chappaz, Alban. "Développement de nouveaux milieux et catalyseurs acides pour la transformation de biomasse lignocellulosique en molécules plateformes." Thesis, Lyon, École normale supérieure, 2014. http://www.theses.fr/2014ENSL0936.
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L'objectif de la thèse est d'étudier la transformation de la fraction cellulosique de la biomasse en acide lévulinique. Cet acide est une molécule plateforme permettant un accès à de multiples produits, tels que des solvants, des monomères ou encore des molécules à plus forte valeur ajoutée.Nous proposons d'étudier la transformation de la cellulose en acide lévulinique catalysée par des solutions aqueuses concentrées en acides de Brønsted. La forte acidité de ces milieux et leur capacité à rompre les liaisons hydrogène de la cellulose rendent possible des réactions à température modérée (80°C), ce qui laisse espérer la production sélective d'acide lévulinique.L'état de l'art concernant la production d'acide lévulinique à partir de glucose ou de cellulose est d’abord présenté, ainsi qu’une étude bibliographique sur les techniques permettant la mesure d’acidité de milieux concentrés.La caractérisation de l’acidité des milieux semblant être un point clé pour contrôler la réaction, la seconde partie concernera les mesures d’acidité des milieux concentrés utilisés. La méthodologie expérimentale pour identifier et quantifier les produits de réaction de la cellulose ainsi que les paramètres critiques qui la régissent sont ensuite détaillés.Enfin l’étude s’achèvera par deux chapitres traitant de la transformation du glucose ou la cellulose en acide lévulinique dans des milieux comportant une forte acidité de Brønsted combinée, ou non, avec des sels métalliques. La transformation du glucose conduit à des sélectivités en acide lévulinique de 50 mol% dans l’acide sulfurique 65 % et supérieures à 70 mol% dans l'acide sulfurique 48 % en présence de chlorure d'aluminium hydraté. La transformation de la cellulose conduit à des sélectivités en acide lévulinique d'environ 43 mol% dans les milieux acides de Brønsted concentrés et 60 mol% lorsque des sels métalliques sont ajoutés. De telles sélectivités en acide lévulinique n'ont jamais été décrites dans les milieux concentrés<br>The thesis presented in this document aims at converting lignocellulosic biomass into levulinic acid. This target is a valuable building block which can lead to various products.This platform intermediate can be obtained by acid-catalyzed conversion of cellulose contained in raw biomass. However, the state of the art concerning this acid-catalyzed reaction revealed that the current conditions (diluted acids in harsh temperature conditions) result in numerous by-products formation. The selectivity issue often deals with process control, in particular with reaction time optimization.Our approach lies in using concentrated Brønsted acids as alternative media to catalyze cellulose conversion. Indeed, the high acidity level allow the interaction with hydrogen bonds in cellulose fibrils and favor cellulose decristallization. This property should promote the transformation of cellulose into levulinic acid at lower temperature thus limiting the formation of by-products. Therefore, acidity measurements in such media have been developed and performed. An extensive study on glucose and Avicel cellulose conversion in concentrated aqueous solutions of sulfuric acid was performed at 80°C. Levulinic acid yields, up to 50 mol%, were determined by HPLC analysis and a special attention was dedicated to the identification and quantification of soluble or insoluble by-products, allowing the characterization of new species never described in aqueous solutions. Referring to the acidity levels previously determined, a comparison between acidity and catalytic results will be setted.Finally, the effect of metallic chloride addition on the transformation of glucose and cellulose in sulphuric acid solutions has been investigated, revealing improvements yielding up to 70 mol% levulinic acid. This range of selectivity is unprecedented at such a low temperature
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Pinheiro, Danielle Lobo Justo. "O uso de azalactonas em síntese orgânica: preparação, aplicação em reações de formação de ligação C-C e em síntese total." Universidade Federal de Juiz de Fora (UFJF), 2018. https://repositorio.ufjf.br/jspui/handle/ufjf/7551.
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Previous issue date: 2018-09-09<br>CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Azalactonas são heterociclos derivados de aminoácidos protegidos e ciclizados. Por conter em sua estrutura um sítio eletrofílico, um sítio pro-nucleofílico, além de um sítio nucleofílico ou eletrofílico (que será determinado pelas condições reacionais), esses compostos são extremamente versáteis. Nesse trabalho é demonstrado a reação das azalactonas com o reagente de Schwartz, que através de uma de redução quimiosseletiva gera derivados de aminoaldeídos com excelentes rendimentos em apenas 2 minutos de reação. Outra reação de redução quimiosseletiva demonstrada no trabalho envolve o uso de azalactonas de Erlenmeyer, hidrogênio e Pd/C como catalisador. Dessa forma, azalactonas saturadas funcionalizadas, foram possíveis de ser obtidas em uma metodologia simples, com excelentes rendimentos. O processo foi ainda adaptado para reações em um sistema one-pot, produzindo assim, adutos de Michael, Mannich e produtos de abertura de maneira simples e eficiente. O sítio nucleofílico das azalactonas também é explorado em reações de dimerização diastereosseletivas, utilizando uma base de Brønsted formada in situ pela reação entre acetonitrila e sal tricloroacetato de potássio ou sódio. O mecanismo da reação e estudos cinéticos são demonstrados a partir de uma análise obtida por experimentos online no RMN de ¹H. Além disso, um análogo de um produto natural é obtido através de uma redução estereosseletiva dos dímeros. O sítio nucleofílico das azalactonas também é explorado em reações de carbonilação α-arilativa catalisadas por Pd, utilizando o sistema de duas câmaras, seguido de sua abertura, obtendo, dessa forma, aminoácidos α,α-dissubstituídos protegidos. O mecanismo da reação é proposto após reações controle terem sido realizadas. Os mesmos aminoácidos também puderam ser sintetizados e marcados com o ¹³C. Esses compostos marcados foram aplicados em reações quimiosseletivas, como a reação de descarboxilação de Krapcho, reduções quimiosseletivas, e síntese de heterociclos como as oxazolonas e pirazolonas.<br>Azlactones are heterocycles derived from amino acids. There are an electrophilic site, a pro-nucleophilic site, and a nucleophilic or electrophilic site (determined by the reaction conditions). These compounds are extremely versatile. In this work the reaction of the azlactones with Schwartz reagent is demonstrated. A chemosselective reduction of these compounds is possible to generate aminoaldehydes in excellent yields in only 2 minutes reaction. Chemosselective reduction of Erlenmeyer azlactones is also demonstrated by using hydrogen gas and Pd / C as a catalyst. In this way, functionalized saturated azlactones are possible to obtain in excellent yields. The process was further adapted to reactions in a one-pot system, producing Michael, Mannich and opening products in a simple and efficient manner. The nucleophilic site of azlactones is also explored in the diastereoselective dimerization reactions promoted by a Brønsted base, affording by the reaction in situ between acetonitrile and potassium or sodium trichloroacetate salt. The mechanism of the reaction and kinetic studies are demonstrated from an analysis obtained by ¹H NMR online experiments. In addition, a stereoselective reduction of a dimer analogue gave a natural product in high both yield and diastereoselectivity. The nucleophilic site of the azalactones is exploited in Pd catalyzed α- arylation carbonylation reactions, using the two-chamber system, followed by their opening, thereby obtaining protected α,α -disubstituted amino acids. The mechanism of the reaction is proposed based on control reactions. The same amino acids could also be synthesized with ¹³C-labeled CO. These coumpounds were applied in chemosselective reactions, such as krapcho decarboxylation reaction, chemosselective reduction, and synthesis of heterocycles such as oxazolones and pyrazolones.
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Bunrit, Anon. "Direct Catalytic Nucleophilic Substitution of Non-Derivatized Alcohols." Doctoral thesis, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-146426.
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This thesis focuses on the development of methods for the activation of the hydroxyl group in non-derivatized alcohols in substitution reactions. The thesis is divided into two parts, describing three different catalytic systems. The first part of the thesis (Chapter 2) describes nucleophilic allylation of amines with allylic alcohols, using a palladium catalyst to generate unsymmetrical diallylated amines. The corresponding amines were further transformed by a one-pot ring-closing metathesis and aromatization reaction to afford β-substituted pyrroles with linear and branched alkyl, benzyl, and aryl groups in overall moderate to good yields. The second part (Chapters 3 and 4) describes the direct intramolecular stereospecific nucleophilic substitution of the hydroxyl group in enantioenriched alcohols by Lewis acid and Brønsted acid/base catalysis. In Chapter 3, the direct intramolecular substitution of non-derivatized alcohols has been developed using Fe(OTf)3 as catalyst. The hydroxyl groups of aryl, allyl, and alkyl alcohols were substituted by the attack of O- and N-centered nucleophiles, to provide five- and six-membered heterocycles in up to excellent yields with high enantiospecificities. Experimental studies showed that the reaction follows first-order dependence with respect to the catalyst, the internal nucleophile, and the internal electrophile of the substrate. Competition and catalyst-substrate interaction experiments demonstrated that this transformation proceeds via an SN2-type reaction pathway. In Chapter 4, a Brønsted acid/base catalyzed intramolecular substitution of non-derivatized alcohols was developed. The direct intramolecular and stereospecific substitution of different alcohols was successfully catalyzed by phosphinic acid (H3PO2). The hydroxyl groups of aryl, allyl, propargyl, and alkyl alcohols were substituted by O-, N-, and S-centered nucleophiles to generate five- and six-membered heterocycles in good to excellent yields with high enantiospecificities. Mechanistic studies (both experiments and density functional theory calculations) have been performed on the reaction forming five-membered heterocyclic compounds. Experimental studies showed that phosphinic acid does not promote SN1 reactivity. Rate-order determination indicated that the reaction follows first-order dependence with respect to the catalyst, the internal nucleophile, and the internal electrophile. DFT calculations corroborated with a reaction pathway in which the phosphinic acid has a dual activation mode and operates as a bifunctional Brønsted acid/Brønsted base to simultaneously activate both the nucleophile and nucleofuge, resulting in a unique bridging transition state in an SN2-type reaction mechanism.<br><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript.</p>
Books on the topic "Brønsted acid/base"
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Maruoka, K., K. Nagasawa, Y. Sohtome, et al. Brønsted Base and Acid Catalysts, and Additional Topics. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-205-00000.
Full textBook chapters on the topic "Brønsted acid/base"
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Hatano, Manabu, and Kazuaki Ishihara. "Brønsted Acid/Lewis Base Hybrid Complexes." In Topics in Organometallic Chemistry. Springer International Publishing, 2015. http://dx.doi.org/10.1007/3418_2015_143.
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Atkins, Peter. "Civil Partnerships: Lewis Acid–Base Reactions." In Reactions. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199695126.003.0013.
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One of the most remarkable chemists of the twentieth century, Gilbert Lewis (1875–1946), who died in a rather peculiar event involving cyanide (which will figure further in this account) took the story of acids and bases that I described in Reaction 2, extended its reach, and thereby captured a further huge swathe of chemical countryside. As I remarked in that section, chemists seek patterns of behaviour, partly because it systematizes their subject but also because it gives insight into the molecular events accompanying a reaction. Lewis contributed greatly to this enlargement of chemistry’s vision, as I shall unfold in this section. I explained in Reaction 2 how Lowry and Brønsted had extended Arrhenius’s vision of acids and bases by proposing that all reactions between acids and bases involve the transfer of a proton (a hydrogen ion, H+) from the acid, the proton donor, to the base, the proton acceptor. For instance, hydrochloric acid, HCl, can provide a proton that sticks to an ammonia molecule, NH3, 1, converting it into NH4+, 2. The Lowry–Brønsted account of an acid–base reaction involves a proton as an essential part of the definition: if protons aren’t around, then Lowry and Brønsted are silent on whether a substance is an acid or a base. There are, however, many reactions that resemble acid–base reactions but in which no protons are transferred. I will give what might seem to be a rather esoteric example, but it makes the point in a simple and direct way, so please bear with me; you will soon see the relevance of this presentation to everyday life. The esoteric example I have in mind is a reaction in which a boron trifluoride molecule, BF3, 3, sticks to an ammonia molecule to form NH3BF3, 4. This reaction clearly resembles the proton transfer reaction in which H+ attaches to NH3 to form NH4+, but with BF3 playing the role of H+. Lewis brought these aspects together in a very simple idea in 1923, at about the same time as Lowry and Brønsted made their proposals. A base, he proposed, is any species that can use two of its electrons to attach to an incoming species.
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Singh, R. P., and L. Deng. "Asymmetric Brønsted Base Catalysis." In Brønsted Base and Acid Catalysts, and Additional Topics. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-205-00058.
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Chen, Y. C., and H. L. Cui. "Brønsted Acid Catalyzed Cascade Reactions." In Brønsted Base and Acid Catalysts, and Additional Topics. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-205-00598.
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Pápai, I. "Organocatalysis by Brønsted Bases." In Brønsted Base and Acid Catalysts, and Additional Topics. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-205-00468.
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Pápai, I. "Organocatalysis by Chiral Brønsted Acids." In Brønsted Base and Acid Catalysts, and Additional Topics. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-205-00471.
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Singh, R. P., and L. Deng. "Acid–Base Cooperative Catalysis." In Brønsted Base and Acid Catalysts, and Additional Topics. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-205-00075.
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Hatakeyama, S. "Using Chiral Thioureas as Brønsted Acid Activators with Achiral Amine Nucleophiles." In Lewis Base and Acid Catalysts. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-204-00336.
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Singh, R. P., and L. Deng. "Enantioselective Base Catalysis." In Brønsted Base and Acid Catalysts, and Additional Topics. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-205-00057.
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Singh, R. P., and L. Deng. "Base–Iminium Catalysis." In Brønsted Base and Acid Catalysts, and Additional Topics. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-205-00095.
Full textConference papers on the topic "Brønsted acid/base"
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Guo, Hong, and Patricia Iglesias. "Tribological Properties of Ammonium Protic Ionic Liquids As Additives in Polyalphaolefin for Steel-Steel Contact." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10645.
Full textAbstract:
Abstract Around 23% of the world’s energy consumption results from rubbing contacts, in which 20% is used to overcome friction and 3% is due to wear and the consequent failure. The implementation of lubricants and effective lubricant additives are indispensable to reduce friction and wear of rubbing materials. Protic Ionic Liquids (PILs), which are easily obtained by proton transfer from a Brønsted acid to a Brønsted base, have shown great potential to be used as lubricants due to their structures and tunable properties. In this study, two kinds of novel PILs, bis(2-hydroxyethylammonium) succinate (DSu) and tri-[bis(2-hydroxyethylammonium)] citrate (DCi), were synthesized and tested as lubricant additives. The tribological behavior of the two PILs is studied as additives in 1 wt. % to a base synthetic lubricant (PAO) for steel-steel contact under different temperatures (room temperature and 100°C) and normal loads (3 N and 4 N) using a ball-on-flat reciprocating tribometer. When 1 wt. % of any PILs is added into PAO, friction is reduced compared to that with neat PAO at all temperatures and loads studied, and good anti-wear performance is also obtained under the higher temperature studied. Particularly, 1 wt. % DCi +PAO shows the best high-temperature tribological behavior under 4N, with friction and wear reductions of 33% and 35%, respectively.
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Liliasari, S., E. Nursa’adah, and L. N. Amsad. "Describing Pre-service Chemistry Teachers’ Misconceptions of Proton Transfer in Acids-Bases Brønsted-Lowry." In 2nd Asian Education Symposium. SCITEPRESS - Science and Technology Publications, 2017. http://dx.doi.org/10.5220/0007301502190222.
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Tsukamoto, Yoshihisa, Takao Fukuma, and Jin Kusaka. "Analysis and Modeling of NOx Reduction Based on the Reactivity of Cu Active Sites and Brønsted Acid Sites in a Cu-Chabazite SCR Catalyst." In 14th International Conference on Engines & Vehicles. SAE International, 2019. http://dx.doi.org/10.4271/2019-24-0150.
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